This invention relates to a method of purifying a dustcoal fed into a steel or iron bath reactor, and an apparatus operating in accordance with the principles of such method.
The continuous gasification of coal or carboniferous fuels in a steel or iron bath reactor is generally disclosed in U.S. Pat. No. 3,533,739. The coal gas issues from the reactor at a temperature of about 1400.degree. C. and entrains large quantities of dust.
Heretofore, the dust content has typically been reduced to a justifiable extent by means of venturi scrubbers, and could be very high in short and large-size gas pipelines between the producing reactor and the consumer. Such pipelines are easy to clean and the amount of dust that settles out of the streaming gas over short distances is only small. Keeping short and large-size pipelines clean can be done with ease and does not interfere significantly with the operation of the active consumers (power stations, push-type furnaces of a mill train, etc.).
However, if the gas produced through a coal gasification is fed into industrial systems or even into long-distance supply systems, which are now coming into wide usage to safeguard the world's energy supply, large quantities of dust can precipitate given the extended period during which the gas is conveyed from the reactor to the consumer. This precipitation is also facilitated by the fact that the gas stands still in the lines at times, because the withdrawal is not continuous. It is easy to understand that, as a result, the lines of the supply systems can become clogged after a very short time. Another determining factor is the fact that conventional gas supply systems are made up of pipes with small diameters. When coal gases that have been purified in a known manner are introduced, it is unavoidable that the gas supply breaks down because of the clogging of the pipes. However, often it is not possible to clean these pipes, or it can be done only with great difficulty, because of the local conditions.
Problems also arise if gas turbines are operated with the coal gases. The requirement here is that the dust content be less than 5 mg per cm.sup.3. Presently, with the venturi dust extractor this limit can be reached only at high cost.
A purifying method is known and described in German Pat. No. 486,912 for purifying hot dust-containing gases, wherein the dust is combustible. According to this method, the hot gas is first cooled, utilizing the heat, and is then purified in an electrofilter. The use of electrofilters for purifying gas is also known and described in British Pat. No. 219,570. However, this known method is not designed for hot gases, so that cooling of the gases being purified is not within the purview of this patent.